text:
Do any flights go over the South Pole?
Are there any flights that go over the South Pole, or any that have? I'm not interested in flights over the edges of Antarctica, I'm asking about crossing right over the Pole.
Are there any problems with the planes compass flying over the South Pole?

Related: Why does no aircraft cross directly over the pole?

There are no scheduled flights but plenty of tour operators will fly you there. Google will help.  Travel.SE would also be a good place to ask, there are folks over there who have done this.

@Simon the commercials only fly near the "beach", they never cross it

@chirlu This question is about the North pole

@mins Don't really want to get into degrees, I'm only interested to cross the island

You haven't looked hard enough.  There are NZ operators who will charter for you.

Only one, but it is a cargo aircraft and it only flies on one night every year.

"the commercials only fly near the "beach", they never cross it ".  As well as the charter and tourist flights, you can fly to Mt Erebus easily.

@Freddy: Yes, but one answer also covers the south pole. And apart from that, it is still a related question that may interest others who find this one.

Please forgive me for asking if you are a "flat earth truther".  We sometimes get those numpties passing by trying to justify their theories (especially the one about Antarctica being a ringed ice wall with the military guarding it to make sure no-one learns the secret).
There have been many flights over the geographic South Pole, the first documented one being in 1935 by Lincoln Ellsworth and Herbert Hollick-Kenyon.  See also the first flight over Antarctica.
Pan Am flight 50, using a Boeing 747SP, also flew over both poles.
No scheduled commercial flights over fly the South Pole since there are no great circle routes in use which do so.
Flights from New Zealand to South Africa would fly over Antarctica but no airline currently flies that route.
As to problems with the compass, modern aircraft have no problems since the primary navigation source is GPS.  If you were using a compass only, as you got close to the magnetic South pole (remember, this is not even in Antarctica), the compass would become increasingly unreliable.  Simply maintain a straight course though, over the pole, and the compass will become increasingly reliable.  However, navigating over the magnetic poles using only a compass is the preserve of explorers and the fool-hardy.
This document contains more technical detail regarding navigation.  It talks mainly about the North magnetic pole but is applicable to both.
A couple of other considerations when asking about commercial flights is the need for ETOPS certification and the need to carry special survival equipment when flying south of latitude 72 degrees which is very considerable and would require the removal of revenue seats to carry it.
There is a big difference between the nearest suitable diversion airport flying over the Arctic and flying over the Antarctic.

lol at the flat earth theory. Thanks a million for your answer!

It looks as if PER-EZE via great circle route comes really close to the pole... http://www.gcmap.com/mapui?P=PER-EZE

Example of navigation issues across a magnetic pole: https://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_902

There are no scheduled commercial flights over south pole- in fact, there are none over Antarctica.
That said, you can fly to south pole in south pole flights. The site specifically says:

Fly to the South Pole, where all 360 lines of longitude meet and in a few steps you can walk around the world.
History comes alive as you stand at 90° South, the ultimate goal of polar explorers Amundsen and Scott.

@aeroalias They take the same way out they came in therefor not crossing it. Thank you for the detailed answer!

@Freddy What exactly are you asking for?  Do you want someone to fly you over the South Pole (in which case, which pole, there are 4?).  The only way you can do that is to charter your own flight.  There are several operators who will do this, here's an example but, this really has nothing to do with aviation.  it's a travel question.  Oh, and please confirm that you are not a "flat earth truther".

@Simon "flat earth truther"? First of all I was wondering why they fly over the north pole but never over the south pole (I didn't find any record). Just curious why they don't go from Australia and New Zealand to South America and Africa to save fuel? I asked it here because I thought it had something to do with magnetic south pole and the planes compass. Don't think they would be able to answer technical part of the question at the travel section.

@Simon Now I just find it weird no one on earth ever flew over (even at high alt) and made a detailed report about it. (if it has happend I'm sure someone would have posted it by now)

@Freddy: The actual location of cities in the southern hemisphere (there's a lot of ocean out there) means that flights don't need to fly over the south pole to save fuel. The shortest distance is called the "great circle". For a flight from say Auckland to Johannesburg, the great circle path only just touches the Antarctic coast. One that comes close would be Perth to Buenos Aires, but no airline flies that route.


text:
Do airlines have contingency plans to keep passengers warm in the event of an Arctic emergency landing (or otherwise a diversion)?
Imagine you're flying to Los Angeles in February, but find yourself landing in Iqaluit instead, with a daily mean of −27.5°C, without considering the effect of wind.  Even walking from the cabin to a runway bus may involve sufficient exposure to cause serious injury if passengers (and crew) are dressed for +20°C.  Most intercontinental flights pass over high latitudes, so a high-latitude emergency landing can't be that exceptional.
Are airlines required to have contingency plans to keep passengers warm in such an event?  There wouldn't be space to stock lots of bulky fur coats on a plane, but groundside there would be.

The passengers can just stay on the plane until a backup arrives.

@JonathanReez If the engines fail it wouldn't stay warm long on the plane either, I guess (this is why Swedish trains get cancelled when it's -40°C), and when it is -40°C, even transferring passengers from one plane to another requires protection from the elements.

There is some info on Wikipedia: The FAA's policy letter Guidance for Polar Operations (March 5, 2001) outlines a number of special requirements for polar flight, which includes two cold-weather suits, special communication capability, designation of Arctic diversion airports and firm recovery plans for stranded passengers, and fuel freeze strategy and monitoring requirements.

It's not a problem for a short while

They can charge $5 for a blanket, discounted due to the outstanding circumstances. (...or perhaps upcharged due to them...)

@CountIblis, even without special meditation, in a cryosauna people can usually handle 1 or 2 minutes at -40–-60°C followed by 1 to 3 minutes at -110–-120°C. That should be enough to get from the plane to the bus or other emergency vehicle.

@gerrit: Even if the engines fail, the inside of the plane is still going to stay warmer for longer than outside it, due to things like all the insulation between the layers of the fuselage, the lots of warm bodies in it, the protection from direct wind, etc., etc., etc..

@Sean Yes, but if the plane cannot be repaired the passengers will eventually have to move to another plane somehow.

Taking FAA/USA as an example.
For north of 78th parallel, FAA operations are conducted in compliance with several regulations, including: FSIMS 8900.1, vol 3, Chapter 18, Section 4  Part B Operations Specifications: OpSpec B055 - North Polar Operations. The alternate airports must be able to receive the passengers of the diverted aircraft and to take care of the "physiological needs of the passengers and flightcrew for the duration until safe evacuation".
B055 requires the operator to demonstrate a recovery plan to extract passengers from a diversion airport prior to conduct commercial passenger operations. While it's the operator responsibility to provide the details, the general requirement answers your question:

A recovery plan is required that will be initiated in the event of an
  unplanned diversion. The recovery plan should address the care and
  safety of passengers and flightcrew at the diversion airport, and
  include the plan of operation to extract the passengers and flightcrew
  from that airport.

As the plan should address the care and safety of people at the alternate airport, any protection against low temperature must be provided in order for the plan to be accepted by FAA. The plan must also demonstrate the ability to extract passenger from the airport within, if possible, 12h (which may be a challenge in Arctic region) and at most within 48h.
Extract of B055 (also discussed at PPRuNe, some copy-paste done from here):
Minimum Equipment List (MEL)

Before receiving FAA authority to conduct polar operations, the MEL must indicate that the following systems/equipment is required for
  polar operations dispatch:
3)    Communication system(s) relied on by the flightcrew to satisfy
  the requirement for effective communication capability.
4)    Except for all-cargo operations, expanded medical kit to
  include Automated External Defibrillators (AED).

Training Program Requirements

The following must be in the approved training programs:

Training on special considerations, such as diversion decision making into austere airport environments to include aircraft
  performance, crash, fire, and rescue availability, and passenger
  support; and
Flightcrew training in the use of the cold weather anti-exposure suit.

Special Flightcrew Issues for Long-Range Operations

The operator needs to address the following special long-range
  flightcrew issues:

A minimum of two cold weather anti-exposure suits will be required to be onboard so that outside coordination at a diversion airport with
  extreme climatic conditions can be accomplished safely.

Dispatch and Crewmember Considerations During Solar Flare Activity

The operator must be aware of the content of AC 120-52, Radiation Exposure of Air Carrier Crewmembers, and provide crewmember training
  as stated in AC120-61, Crewmember Training on In-Flight Radiation
  Exposure.

En Route Polar Diversion Alternate Airport Requirements

Operators are expected to give definition to a sufficient set of alternate airports for polar diversions, such that one or more can be
  reasonably expected to be available in varying weather conditions.
The flight must be able to make a safe landing, and the airplane maneuvered off of the runway at the selected diversion airport. In the
  event of a disabled airplane following landing, the capability to move
  the disabled airplane must exist so as not to block the operation of
  any recovery airplane.

In addition, those airports designated for use must be capable of protecting the safety of all personnel by being able to:
(1) Offload the passengers and flightcrew in a safe manner during
  possible adverse weather conditions;
(2) Provide for the physiological needs of the passengers and
  flightcrew for the duration until safe evacuation; and
(3) Be able to safely extract passengers and flightcrew as soon as
  possible (execution and completion of the recovery is expected within
  12 to 48 hours following diversion).

Validation Flights

An FAA-observed validation flight is required in which the operator exercises its reaction and recovery plan in the event of a diversion
  to one of its designated en route polar diversion alternate airports.
  The exercise of the operator’s reaction and recovery plan may also be
  completed prior to the validation flight.

I believe this answer can be improved by making it shorter, i.e. keeping only elements directly related to the question, and offering a link to readers who are interested for more.

@kevin it is fine, the skimmers and TLDRers can go to a crash landing north of Iqaluit (nothing against Iqaluit). The problem with migrated questions is, they were tailored to a specific stack mindset, and then after migrated they are a poor fit on the host stack. mins errs on the side of completness, and that is not an err at all.

@kevin, Mindwin: I agree with both comments, and removed some details. I can edit further (or you may also edit) if you have other ideas, or in case of OP's request for clarification.

This answer seems almost entirely off-topic, since it is about regulations that apply north of 78°N, but Iqaluit is at only 64°N! A flight that doesn't get anywhere close to 78°N, and is not subject to any of those regulations, could still have to divert to a very cold place like Iqaluit.

You've actually answered your own question in a way.  It's the airport's responsibility to be able to operate in such conditions, including accepting diversions by accommodating all international air transport standards.
But, since such an event is extremely rare, there are certain things that have to be figured out on the ground, such as what to do when ambient temperatures are −27.5°C.  Unless there is imminent danger, remaining on the aircraft is an option until a means to transfer passengers to the terminal is sorted.
In the case of LX40, Iqaluit receives regular passenger service so only the number of passengers is exceptional, not the conditions.
"But what if it's a blizzard?!"  Such extreme conditions would make the landing itself unsafe so the crew would have to select another location.
Note:  Since there is not explanation for the Downvotes, they should be treated as wrong and misleading.  Ignore.

-30°C is not extremely rare at Iqaluit, and passengers planning to travel there will have planned for it.  How rare are winter emergency landings at Arctic airports, that is a different question.

I guess emergency landings at Iqaluit are rather rare.

The airlines and manufacturers work very hard to make sure they are extremely rare.

@Johns-305: The reason may also be a health problem with the crew or a passenger (e.g. heart attack). There are cases for both.

Airports have a certain responsibility, but ultimately it is up to the airline to have recovery plans in place (which is the original question). For US flag carriers, it's one of the specific requirements for approval to operate in Arctic regions in the first place (see Mins' answer above).

@PHChilly Well, not really.  It is still the airport's responsibility to maintain it's own equipment.  If for whatever reason they are no longer able to support a diversion, such has having no facilities to service passengers, the airport has to make notification so that it is no longer considered a suitable alternative.

All true, but the question is about what plans airlines are required to have for Arctic ops.

"Iqaluit receives regular passenger service so only the number of passengers is exceptional, not the conditions" -- but the point is the unpreparedness of the passengers (no coats). 2. "Since there is not explanation for the Downvotes, they should be treated as wrong... Ignore." -- I didn't DV, but I don't think there is any requirement to explain DVs. And I don't understand what exactly you mean by saying they should be "ignored". They certainly won't be ignored by SE's algorithms. What exactly am I supposed to do as a reader of your answer in order to pretend DVs didn't happen?

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sort: votes


text:
How is cloud height measured?
In general, cloud height is measured from ground or AMSL (above mean sea level)?
If they measure from AMSL, how are low level clouds' height measured in higher terrain?

Cloud ceiling is measured from ground:

height of the base of the lowest clouds ... that cover more than half
  of the sky ... relative to the ground

Cloud base is measured from sea level:

... the lowest altitude of the visible portion of the cloud. It is
  traditionally expressed either in m or feet above mean sea level

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text:
How much air, by mass, enters an average CFM56 turbofan engine cruising per minute?
How many kg of air enters an average CFM56 turbofan engine cruising per minute?
I have looked everywhere and cannot find it or figure out how to find it, if you could either tell me or give advice on where or how to find it I would appreciate it. Thanks

A reasonable first approximation would be the mass of air that the engine flies through in a minute - i.e. frontal area of the fan blades $\times$ aircraft velocity $\times$ air density. As a sanity check on your estimate, though at different conditions where the inlet velocity is not equal to the aircraft speed, at takeoff each engine on a B747 generates about 200kN of thrust, with an air mass flow of about 1 tonne (1000kg) per second.

Aviation.SE is the right place to ask this.

When you say "how much" do you mean by mass or by volume?

@TomMcw It was originally kg but someone altered it

@SRawes Put that back in :)

Airflow at takeoff
The CFM56-5C, the largest CFM56, powers A340. Its thrust is about 145 kN at takeoff. It has an air mass flow of 485 kg/s (source). A A340 has four engines.

CFM56-5C, source.
Fortunately this thrust is not needed after takeoff and the engine airflow is considerably lower in cruise. I don't have the actual figure but we can do a quick estimate using the fuel consumption. It can be assumed relatively safely that air is in proportion of fuel.
Fuel consumption
According to this document, for the CFM56-5C:

T/O thrust is 150 kN, fuel consumption 2.3 kg/s
Cruise thrust is 40 kN, fuel 0.5 kg/s.

(meaning cruise at 27% T/O thrust requires 22% of the T/O fuel, the engine is more efficient in altitude.)
Airflow in cruise
So we can roughly estimate air mass flow in cruise to be about 485 * 0.22 = 107 kg/s.
This is supported by figures found online in non authoritative sources, like page 245 of this book:

Bypass flow vs core flow
After the fan, air is separated in two flows: core (hot/primary) and bypass (cold/secondary) according to the bypass ratio.
The CFM56-5C bypass ratio is 6.4:1. So:

The part used in the core for combustion, bleed air and core cooling is 485/7.4 = 66 kg/s

The part bypassing the core, and providing only thrust by fan acceleration is 419 kg/s.

For comparison the Trent XWB (A350 XWB), a larger engine developing 430 kN at takeoff, has an air mass flow of 1,440 kg/s (source).

will that not be different at a cruising altitude @mins

Is this figure the amount passing through the intake, or the amount passing through the combustion chamber?  Can you break down the two for a feel for how much air is bypassed?

@SRawes: Yes, this is the maximum thrust/airflow. I have updated the answer.

The specific fuel consumption at cruise you give is suspect. The thrust-specific fuel consumption of high-bypass turbofans should increase with speed. This table gives $33.7\ \frac{\mathrm{g}}{\mathrm{Nh}}$ static and $55.6\ \frac{\mathrm{g}}{\mathrm{Nh}}$ at cruise. The power-specific fuel consumption still decreases, so propulsive efficiency increases, but 27% thrust for 22% fuel seems wrong.

@JanHudec: Thanks for the remark. The different sources I use are obviously not related to the same CFM56-5C customer version. However, the variations are not either extremely large, and the approximation seems to be still correct. So except for the 27% vs. 22% non essential comment, I believe air quantities shown 485/107 kg/s are correct (I'll update them if someone can point me to complete CFM56-5C specifications).

@mins, I would really love to see a (more) complete specification of the engine too (I would like to improve the rather poor simulation that flightgear uses), but so far never seen it.


text:
How do you calculate the true bearing from a station (QTE)?
Assuming that :

You are flying on a compass heading of 141°,
The compass deviation is given as +3°,
The variation read on the chart is 3° East,
The wind correction angle is +10° and
The relative bearing to the airport is 307°

what would the radial from the station be to the true north?
I thought QTE was a standard term. I did not know that American pilots did not know it.
*QTE: True Eminent from station — What is my true bearing from you? QTE = Reciprocal of true bearing to station.
To derive the true bearing I did the following.
I assume that since compass heading is 141° and deviation is +3°

Magnetic heading should be 141-3 = 139°
True heading (would be without the variation given as 3°E) = 139 +3 = 141°
True bearing to station = True heading + relative bearing = 141+307 =  448°
True bearing = 448-360 = 88°
True eminent from station = 268°

However the answer given is 274°.
I want someone with more aviation knowledge to tell me if I am wrong and if so, where is the "break" in my logic?

Reason for question: Navigation problem with an answer given, however I believe the answer to be wrong - Needed an expert opinion.

Welcome to Aviation.SE, can you give a bit more information about your question? It sounds very much like an exam question. What have you tried so far? I'd recommend you read the [help] for information on what you can ask here and what makes a good question.

Also welcome to Aviation.SE. These kinds of questions are often frowned upon because you need to show some effort and ask specific questions about where your methodology may be flawed. Please give us as much as you can work out and explain where you are stuck. Just giving you the answer doesn't help you understand, and it isn't within the scope of the site to work through the process just given the exam question. Don't get discouraged, you can edit this into an acceptable question!

Welcome to aviation.SE! We have no problem with calculation questions in general, but I suggest you give a little more information. For example, "QTE" means nothing to American pilots. It would be great if you could explain/link to more details. It would also help if you explain why you can't do the calculation yourself, e.g. you can't find the formula; or you can find it, but it gives the wrong answer for you.

Hi, I elaborated the question. I hope now it is more easier to understand. Thanx

Thanks for the edit. I changed the header so it doesn't sound like a homework question. It might attract more answers that way. It you don't agree with the edit feel free to roll it back. I've drummed up some reopen votes. I think it just needs one more

Are you sure "eminent" is the correct translation? I never heard it before (but English is not my primary language) and a quick search retrieves nothing in the context of navigation, but your question. Maybe you wanted to say "emanation" (which seems to be more mnemonic for QTE than an actual signification, and is not broadly used). Related discussion here.

I agree with @mins. The Q-codes don't usually stand for anything in particular. A series of them will be assigned for different types of use and the series will proceed alphabetically. So it appears that QTE indicates true bearing and "eminent" is just a pnemonic. That's my bad, I'll edit the header to reflect that.

You are quite close to the answer, you just made a mistake with the sign of east compass deviation, hence underestimated the true heading by 6°. The actual angles are like this:

The compass deviation is given as +3° while it should be given as 3° east, like the variation. It could be misleading.
Exactly as you then developed, the unknown yellow angle is equal to:

True heading + (relative bearing - 180)
147 + (307 - 180) = 147 + 127 = 274°

What did you use to create the image? Looks good and very helpful.

The error was in the compass deviation.  He subtracted 3 deg from the compass heading when he should have added it.  Compass heading + Compass deviation = mag heading.

@Gerry. Corrected, thanks!

@Notts90: There is a very good open source to produce SVG (vector) graphics: Inkscape. This is a good example of how to use some relatively simple vector tools.

I found this answer and think it could be explained a little different to the answer above which is perfectly correct to see the difference between compass/magnetic/true north moving inversely to true/magnetic/compass heading.
I think one part to understand this is, that headings behave different to the north positions. The best way I have found to remember calculating correct headings is, to start with true heading (TH) and continue to magnetic heading (MH) and then to compass heading (CH). Everything else can be computed from this sequence of two formulas:
TH - variation = MH -> MH - deviation = CH
So:

compass heading is referenced to true north
magnetic heading is referenced to true north (compass + deviation)
true heading is referenced to true north (magnetic + variation)

or the other way round as in the the other answer:

true north is referenced to true heading
magnetic north is referenced to true heading (true - variation)
compass north is referenced to true heading (magnetic - deviation)

I hope this picture visualizes all the concepts:

This still means, that magnetic north in this example is to the east (3°E or +3°) of true north, and compass north is to the east (3°E or +3°) of magnetic north. So if you think about it, moving the north pole further east, reduces the compass heading by the variation and deviation, but only relative to the true heading. And moving the heading towards eastern variation or deviation reduces it as well, but only relative to true north.
So overall the phrase "east is least" can be seen and understood that way.


text:
What's the relationship between FANS and CPDLC?
I'm confused about Future Air Navigation System (FANS) and Controller–pilot data link communications (CPDLC). Someone said FANS includes CPDLC, another said it does not.

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text:
Can a holder of a G4 Visa legally receive flight training and/or acquire a Private Pilot Licence?
I am planning to attend a flight school and acquire a PPL, but I am currently staying in the US with a G4 Visa. Am I allowed to receive flight training legally?

You would need an M-1 (for training at a flight school) or F-1 (for training at a college & some flight training academies) Visa to receive flight training.
More information here.

The link you give cites a regulation that prohibits B-1/B-2 visitors from enrolling in school (because those are visitor visas), though recreational studies, if you're just taking lessons for fun, can be a separate thing. This document seems to indicate G-4 holders may be able to study. The bit I have no idea about, and why I never answered this question, is whether a G-4 holder can get TSA Alien Flight Student Program approval with a G-4 for flight training.

While it does not specifically address the GV visa, it does state: "The alien may not enroll in the course of study until the Service has admitted the alien as an F-1 or M-1 nonimmigrant or has approved the alien's application." It also goes on to say the H-type visas can also be used for flight training, however it still says nothing about the G-type visa.


text:
Could the GPS be used to aid the autopilot with speed?
In the AF447 incident, the autopilot system was offline due to the aircraft's pitot tubes being obstructed by ice particles.
Since the physical condition of the plane in air is cold and risky, the same physical obstruction could happen again and again.
Though the pilot is trained to fly the plane in bad weather, I'm wondering why not just use the GPS to aid the plane's computer? The GPS system could be a secondary source to providing the computer with information for flying, like speed and altitude.
If the GPS could've aided AF447 in preventing the autopilot system from going offline, would the pitot's issue not to initialize the system problem then crash a plane?

GPS speed is already available to the crew, although not in an easy to see place.  It isn't designed to cross-check other instruments because it is showing entirely different information.  The winds are changing the actual speed of the airplane across the ground (which GPS shows) and altitude affects the air density (which changes the airspeed shown on the airspeed indicator).  The difference between the two can be vast, with no easy correlation.  Altitude has similar issues, although not as severe.
Even if they could be "synced up", the problem comes in when there is a difference between the two.  Which do you trust?  GPS receivers can (and do) fail, and could show an incorrect speed as well.  When the computer gets conflicting information like it did between the different systems in the AF447 accident, it gives control to the pilot to sort out.
From the time that the autopilot disconnected until the ice blocking the pitot system melted away, only 12 seconds passed.  During that time the crew stalled the airplane and then a chain of events ultimately resulted in the crash of a perfectly functioning airplane.  The exact same thing had happened numerous times before then without resulting in a crash.
After the fact, the NTSB identified numerous factors and made recommendations to improve crew training (which has been implemented) and hardware/software modifications to the airplane.  Aviation very much takes a "continuous improvement" view of things, trying to learn from every accident and to try to prevent the same thing from happening again.  Based on what I've seen, I doubt that this exact same scenario will play out again.

On the Airbus system (and most modern Airliner ones) the ground speed, derived from GPS and INS, is in a relatively easy to see place in the corner of the navigation display, together with calculated true airspeed and wind speed. But you are right that it's not much use.

Add that GPS speed is not measured but calculated as the difference in location and time between two position measurements. In my experience GPS speed fluctuates wildly between samples, so it has to be filtered to seem steady This makes it less useful as input. When learning to fly small planes, one exercise was to fly without any instruments at all, only listening and feeling. It works there (in good weather), but probably would not work on a commercial jet.

The main issue is that we can only get groundspeed from GPS data. Winds aloft aren't known exactly at a particular place, so they could be rather inaccurate -- certainly not enough to leave to the hands of the autopilot. The decision to use GPS data to verify airspeed would lie in the hands of the crew. Anyway, they were too preoccupied to go and check that their ground speed was sort of accurate.
It's not uncommon for winds aloft to reach speeds between 180 and 200 knots. While previous weather reports can be useful, winds can change quite frequently -- the chances of the wind changing is much more than the chances of all the sources of airspeed becoming unreliable.
GPS data is also not 100% accurate, so keep that in mind, especially if only some of the sattelites can be reached.
What the crash came down to was mainly a loss of situational awareness, combined with their lack of experience with actual stall recovery, was the main contributing factor to the accident.

and increasing the crew workload by giving them an extra source of information to monitor and verify would have made their problems even worse...

In the AF447 incident report, the speed of AF447 dropped sharply from 274 knots to 52 knots. And, the pilots lost all of information which can tell them the speed. In such case, GPS can give important information (ground speed) in the situation at which the pitot tubes not function. The tubes can be frozen easily, but GPS will be more reliable in the very cold environment.

@CrayKao: the pilots already have GPS information available, but it'd be stupid to use that for automatic control.

The important quantity, measured by pitot probes, indicated airspeed, is not a speed at all. It is a dynamic pressure. Since lift also depends on dynamic pressure and angle of attack, the right backup is angle of attack indicator. In fact it is angle of attack that matters most, but it can't be measured as precisely, so airspeed is used as primary indicator. All transport category aircraft are equipped with angle-of-attack vanes.

But not all of them have angle of attack indicators in the cockpit.

But consider a spiral dive-- angle-of-attack indicator might show "normal", but due to the excess loading, airspeed would be high-- GPS might arguably help here, if pitot system has failed --


text:
How can you do preflight fan inspection when it's windy?
While sitting, bored to tears, intermittently scanning the 'Delayed' display next to my flight, I've looked out of the airport windows.
Out on the stand, amongst the baggage and fuel truck activity, I've seen a technician examining the engine fans with a torch (flashlight), presumably part of a mandatory pre-flight inspection procedure, looking for FOD, cracks etc.
It occurred to me: What does the techie do on a windy day when the fans are spinning too fast to examine by eye?  Is there some way of braking the shaft to stop the windmilling?

... or a strobe light?

A techie with a real torch would be nice to post on facebook :)


text:
What was enabling control to the pilot on the Snecma C-450 Coléoptère?
Looking at the Snecma C-450 Coléoptère, I was wondering about the (4?) fins towards its tail:

Source: Wikipedia
Were they able to pivot to help the pilot control the aircraft?
If not, what else was enabling control to the pilot ?

That is one scary looking aircraft, it just screams unstable.

@GdD It was put down after it tried to kill its test pilot.

@GdD For some reason, I imagine it rolling off the side of the not-perfectly-level runway and toppling when two castors dig into the grass.

The fact that someone actually flew in that thing is amazing.

Wait, is that even real?!?!?     That's one odd looking aircraft!

@mins The technology demonstrator used before the Coléoptère was just that. A Big reactor with a seat on top: https://en.wikipedia.org/wiki/SNECMA_Atar_Volant

Great find, a vehicle with so many new design features in a time before Computed Fluid Dynamics, and hard to test in a wind tunnel where the device could only be mounted in a fixed position.
From this source:

Takeoff, hover, and landing were controlled by deflecting vanes in the engine exhaust: in horizontal flight by four fins mounted just above the castoring landing gear, and in the transition to vertical flight by two retractable canards in the nose.

This source states that the four delta surfaces were movable and were to be used to control horizontal flight. They were puny though, and mounted quite close to the aircraft roll axis. One of the problems encountered during test flight was a slow uncontrolled roll.

For the control of the aircraft in fast flight, there were four cast solid control surfaces allowing in-depth aerodynamic control (horizontal control surfaces) or in rolling and direction (vertical control surfaces). For the phases of vertical takeoff and landing, control was ensured by deviation of the jet (pitching and lace) and of compressed air coming from the compressor (rolling).

The same source has a frontal view of the craft:

So yes the four delta surfaces were able to pivot but were obviously inadequate for providing any control at low speeds. Thrust vectoring was required for slow flight.

The front view is truly a great help, thanks !


text:
Can SID/STAR have shortened names?
I have a strange naming difference for a SID in a route. The route is:

DOME4W DOMEG Y841 ANAVI DCT NVO UM170 KENUM UM615 IDOSA UN857 RESMI
  UN491 DITAL UN872 DIDAK UZ15 ARDOD A5 VALAX VALA1A

I am bothered by the DOME4W departure (Paderborn Lippstadt, EDLP). The actual name is DOMEG 4W.
Is it allowed to have shortened SID names? In the FMS, I see this as well as DOME4W, but the SID description name it DOMEG 4W. Why this difference?

Which aircraft / FMS are you talking about?  Some FMS's may have a limit on the number of characters displayed.

According to the Jeppeson chart legend[pdf] those are database identifiers. I'm presuming that's what would show on a menu in the FMS.

See also the NATIONAL 7 departure from KDCA. Database ID is NATNL7 but the published name is longer.  "Yes" is exactly the correct answer here.

Great! This is awesome info... but.. I am not allowed to use this in filing a flightplan I would assume, but would have to use the full identifier?

It would probably depend on how you file the plan. If you file electronically I would presume the system would give you an error if it didn't recognize the format. If you're filing by voice I'd say the full id would be best.


text:
Why the pitch rate q is zero while angle of attack is changing and vice versa?
In the book Dynamics of flight, the authors present how the pitch rate q and the angle of attack $\alpha _x$ may vary:

Source: Dynamics of flight: Stability and control,
Bernard Etkin, Lloyd Duff Reid, 1996.
Why is the pitch rate q null while the angle of attack changes, and vice versa?

No sir not exactly , i'm asking about the concept of relation between pitch rate and angle of attack .

Why the pitch rate q is zero while angle of attack is changing and vice versa?

It generally does not (*). You misunderstood the statement in the Etkin's book.
The image you posted come from the chapter about "the $q$ derivatives" $C_{L_q}$, $C_{M_q}$ and $C_{h_q}$.
The book is quite explicit:

These derivatives represent the aerodynamic effects that accompany rotation of the airplane about a spanwise axis through the C.G. while $\alpha$ remains zero

It then presents

Figure (b) shows the general case in which the flight path is arbitrary

(this is the figure you posted)

This should be contrasted with the situation illustrated in figure (a), where $q=0$ while $\alpha$ is changing.

The book in no way implies that either one case or the other is true, it is only presenting contrasting academic examples to illustrate the concept of what the $q$ derivatives are.

(*): I said generally because the book itself present one case where you CAN have constant $q$ and $\alpha = 0$, the steady pull-up.
Again, this in no way implies that you always have

q is zero while angle of attack is changing and vice versa

'q' is the pitch rate....rate of change of pitch angle, i.e d(theta)/dt.
Pitch angle is the angle between aircraft reference line and horizon.....
In the first image, the pitch angle of the aircraft is zero (as nose of aircraft is aligned with the horizon)....So, pitch rate is zero....
Angle of attack is an angle between aircraft reference line and velocity vector...In the second image, angle of attack is zero as the aircraft nose is aligned with the velocity vector .....

this explains the terms employed, but does not actually answer the question asked (or explain the misunderstandings behind the question)


text:
What methods are used to make a turbofan engine spool up quicker?
In cases such as a low altitude stall the quick application of power might get a pilot out of a sticky situation, but turbofan engines are fairly sluggish in increasing thrust. If throttle is applied to quickly it can even cause a surge. I'm assuming the problem is the inertia of the fan and compressor. What things do engine manufacturers do to make the engines more responsive? What are the tradeoffs? Do other types of engine (turboprop, turbojet, etc.) suffer from the same problem of delayed response?

See also: Why should jet engine throttles be moved smoothly?

All turbine engines spin up (relatively) slowly, so the answer to the last part is "yes" for turbojets and turboprops. The rest of the question seems like it's asking for a list of suggestions that would be overly broad for a single question.

@reirab not suggesting anything. I'm no engineer. Just wondering what the engine makers do to try to help with response time. Read on a web page, I think p&w where they said their spin-up was quicker but not certain how they did this.

@fooot That's the very question that led to mine.

From memory so take this with a grain of salt. The first 727s had a 7 second spool up time from idle to max power, and there were at least a couple of incidents where aircraft landed a little short. The fix was to have two idle positions, flight idle and ground idle. Simply put, flight idle wasn't the full idle you got in ground idle.

Several things come to mind, but they will all reduce efficiency and/or cost money, so they will not be popular with engine users:

For turbofans: Reduce the rotational inertia of the spinning parts by reducing the bypass ratio. Inertia is mass times distance, so making the engine diameter smaller should have the biggest effect.
Increase temperature margins for the turbine. Today, the electronic control (called FADEC for Full Authority Digital Engine Control) will limit the amount of fuel that can be injected into the combustion chamber to limit the temperature in the turbine. By running the turbine hotter for a few seconds the turbine torque can be increased, at the cost of a reduction in the lifetime of the turbine.
For turboprops: Reduce blade pitch momentarily to unload the propeller, so more torque is available for spooling up the engine core. This, however, reduces thrust when it is needed most.
Reduce secondary loads by disconnecting generators and closing bleed valves. This is already done by todays engine control, however.

The best way of dealing with the slow engine response is operational: Avoid situations where the need for a rapid spool-up might arise or enter those situations not with engines set to idle, but to some medium power setting. Carrier pilots do this routinely by spooling up the engine shortly before touchdown, so they will have the required thrust at their disposal if the tail hook fails to catch any of the arrestor cables.
Thanks to RalphJ for pointing out that turboprops use the same tactic. Helicopters never let the engine run in idle while in flight. If less thrust (turboprops) rsp. lift (helicopters) is needed, both adjust pitch to set the desired thrust/lift and keep engine RPM up. Now the mass flow through the engine core is the same as at full thrust, only the amount of heating in the combustion chamber is reduced to adjust the power output of the engine. When more thrust/lift is needed, the pilot adjusts pitch and fuel flow to set the desired thrust/lift level. Since the engine is already running at top speed, the change is not delayed by inertial effects.

Reduce secondary loads by disconnecting generators and closing bleed valves. This is already done by todays engine control.     Are you talking about something the engine control does routinely when systems are unneeded or is this something it will do if you suddenly ask for more thrust?

@TomMcW: Both, but hull pressurization and ventilation normally need constant bleed flow. Interrupting this for several seconds is not a problem, however, and as soon as the engine delivers full power, the bleed valves open up again.

For turboprops: run at 100% RPM always, and include throttle anticipation in the electronic controls for the blade angle. This gives turboprops essentially instant response (i.e. T56 engine in the P-3 and C-130).  Slow spool-up times aren't nearly so much an issue for today's turboprops as they are for jets.

Also, for aircraft equipped with adjustable exhaust nozzles, reducing the size of the nozzle opening (for non-afterburning flow) will result in a near instantaneous increase in thrust.


text:
When would these two fixes at KMEM be used?
When flying IFR into a class B airport you usually file a STAR at the end of your plan. After the last fix on the STAR you will then receive vectors from ATC to the approach for the assigned runway. At that time you would use the appropriate approach plate for information to complete the approach.
I was looking at some of the approach plates for KMEM and some of them contain multiple IAF's. For example, if you are coming in on the HOBRK 1 STAR and are assigned 36C it says that you should turn right to 53° and expect vectors after ROCAB.

But when you look at the approach plate for 18C you see two extra IAF's, OWAFO and IHTEM being approached directly from the UJM and HLI VOR's respectively.

If one should expect to be on vectors by that point when would these other two IAF's be used?

I'm pretty sure that's just for RNAV approaches - for ILS approaches, turbines follow 55° from TAMMY and are then vectored to intercept the ILS and hence straight-in, but for RNAV approaches, turbines go via OWAFO and then FREAZ, NESBT or HADAN according to selected runway. But I'm no expert!

@user52723a Glad you pointed that out. I selected the non-RNAV STAR. I'll change it or for the HOBRK 1 rnav arrival. Very similar, though. For north ops it starts with vectors at the ROCAB fix, which is right near TAMMY. So that still doesn't explain it if they're coming off an rnav arrival. I never hear ATC mention them at all. Although, admittedly, pretty much all the AC arrive RNAV then pick up the LOC. When using parallel runways I think once they are on the LOC they can reduce required separation

Note that the "expect" clearance is only for situations where there is no radio communication for the crew and they need to know what you are going to do after completing the STAR.  In "real world" ops, they may indeed clear you to one of the other IAF's, or maybe you aren't even flying a STAR because you are repositioning from a nearby airport or are in an aircraft which doesn't fly that high.  All are situations where the feeders may be used for efficient use of the airspace.


text:
Can you file an open-ended IFR flight plan?
Say you are doing an instrument training flight with a CFII and you are practicing IFR navigation. You will be taking off and returning to the same airport, but you are not certain exactly where your CFII might have you go. For instance, your CFII wants to see how you handle deviations in flight. Ths is just an example as I'm sure there are other reasons one would need to be IFR without a specific routing or destination. How would you file such a flight plan? Can you file an IFR flight plan without a specific routing?

Another reason I can think of would be a test or acceptance flight that needs to be conducted in class A airspace. You would have to be on an IFR plan to fly there, but your ultimate destination would be right back where you came from. You might not be able to indicate specific waypoints, etc., instead you would be requesting block altitudes, etc. if you need room to perform maneuvers.

Military folks run into a similar issue when filing IFR to/from working areas (R-areas and MOAs) -- basically, they wind up with a flight plan in two halves at that point...

When you open your IFR flight plan, ATC and you have a contract. You promise to follow the plan and they promise to keep other IFR aircraft away from you. In order for that to work, they need to know where you are going. Also, in the event of lost comms, they need to know what you are going to do. You should file to an airport or a waypoint that is guaranteed to be VFR and then amend/cancel your flight plan if you want to practice deviations.

You could file to terminate at a fix.  You would be within the "real" ATC structure until you reach the fix at which point your CFII would simulate further ATC instructions.

You can file a flight plan with the same departure and destination.

Related-- I hadn't seen the present question when I asked this one-- https://aviation.stackexchange.com/questions/56680/in-the-us-is-there-a-way-for-a-pilot-to-legally-maneuver-at-will-in-actual-im

ERAM (the flight data processor located in the ARTCCs) will accept the following route format for military aircraft (and I suspect civilian as well): KABC KDEF/D0+15 KGHI/0+15 KABC. This tells the computer that you'll depart and land at KABC and will have a 15 minute delay at the middle two airports to execute a practice instrument approach. You can adjust the times accordingly.

If operating within a single area (TRACON) then file from KABC -> KABC and in remarks put "Practice APCHS KXYZ KDEF".  The controller will be asking you what your next approach will be at some point.
Another tactic is to file to ABC VOR (or some other fix) and request a hold. I like this method, as the student gets a hold with an EFC and that gives me time to decide how many orbits they will need as well as the next approach request. I normally have the student ask for the next approach, as it keeps their workload up.
The first suggestion is generally preferred because in the event of lost com, in a true IMC environment, it is clear that you will be returning to KABC, unless you encounter VFR first.
Remember that an IFR clearance can end at a fix (even a pilot defined fix) and when you are in VMC that can be useful. Similarly, an IFR clearance can begin at a fix, and that can be accomplished in a non-radar environment.
Addendum #1
Frequently this type of plan is often referred to as a tower clearance, or if it spans TRACONs it may be called a tower-to-tower.  However, where there are no local approach facilities, center handles this type of clearance as well. Other than just normal approach practice, an area clearance is used to permit photographic missions with cloud cover and instrument student experience with lake effect icing.  For example, a photographer wanted photos of a water fall, through an opening in the clouds.  We got on top, stayed IFR, and maneuvered for his shots.

For air work IFR, there's also a quadrant clearance: "Cleared to fly [NE, SE, SW, NW] quadrant of [or between XXX and XXX radial of] ABC VOR between YY and YY DME at ZZ thousand block ZZ thousand." Quadrants are specifically described in the P/CG. You're not likely to get this if there's a lot of other traffic around.

JScarry's comment is the answer.
The system has multiple levels of safety and assumes that if communications are lost, you'll fly the last clearance.
For instrument training or test flights, you can file a flight plan from airport A to airport B via VOR XYZ or airway V-99. Fly the clearance you receive, then, before you land at B, ask for more clearances to fly to airport C or repeated approaches to B or whatever you want to do.
You will get clearances that always have a valid ending and allow ATC to work out what you will be doing and keep other traffic away from you should communications be lost.
The system was designed when radar coverage was not as extensive as today and radios were not as good as today.
Update to my answer:
If you wanted to do approaches at, say, three airports then fly back home, you can file a flight plan with those airports as points on the route, and with you home airport as the destination.  And put in the Remarks section that you intend to fly an approach at all three airports.  Also, tell the approach controller at each that you intend to do a low approach or touch and go then he or she can ensure your flight plan is not closed at the intermediate airports. There is a good discussion of this subject in Opposing Bases podcast number 257 here: Opposing Bases
And, don't hesitate to call your local ATC center on the phone (from the ground) to ask them how they would prefer you do this kind of thing. They are always happy to give advice and let you know how to do things to make things easier for them and you.

Today when? Last time my wife and I went up the audio panel went out and we had no TX on either radio. Luckily we had a handheld. We were both lapsed pilots from the 90's, and we joke that we flew old airplanes then, but we're still flying the exact same ones now.

@Bill Your correct.  And I've twice lost all comms in this modern era.  Once an electrical problem at a single point of failure left me with no radios, no lights, no nothing - at night.   So as you imply, we do still need to do it like this so that ATC knows what we're going to do if they cannot reach us.

You usually file a local IFR for this kind of flying, usually with a flight plan indicating the airports you will be flying approaches into or other details about your flight.  ATC will generally clear this depending on the airspace, workloads, etc.


text:
Why do older students take longer to learn to fly?
I have heard or read many CFI’s say that older students take more time to learn to fly. I know that as we age our brains in general have more difficulty learning new things, but what part of flying is it that usually takes longer for older students? Do they have more trouble learning things like procedure, regulations and aerodynamics or is it the physical coordination of controlling the plane, judging distances, etc. that takes longer? Maybe it’s the multitasking involved?

"All CFI’s say" - that's a pretty bold assertion

@SteveKuo Ok, All CFI's that I've ever heard or read that have made any observations on the matter. I'll make it less of an absolute.

Slightly related

Depends upon what you mean by ‘old’.  The average student undergoing flight training is in their 30s.  Everyone is also different and, since there is such a diversity of subject to learn in flight school students can have difficulty with lots of different subjects.  Something that comes naturally to one student will be difficult to another one to learn.

@CarloFelicione Obviously everyone will be different. I'm just trying to gauge whether it's usually more of a cognitive thing or more of a coordination thing. The cost of flying lessons is prohibitively high for me already. But from things I've read it seems like it might turn out to be even more of an obstacle. I'm not a senior by any means, I'm fast approaching 50. But that's about the age group many cfi's observe take about 30-50% longer.

Adults, I don’t think, take longer to learn than younger students, but they do learn differently and for different reasons pp 1-10 of the Aviation Instructor’s Handbook addresses these differences in detail.  All in all, adults are much more practical and proactive about their learning and generally better motivated to do so that with younger students which may be doing so at the behest of their parents, etc.

Perhaps it's a simple matter of priorities?  When you're younger, you can basically devote 100% of your free time to flying lessons.  When older, you probably have family responsibilities and other distractions.

This question is more related to human aging and learning than it is to aviation. When people age, there is a toll on several parts of body and the acquired skills may not stay as sharp as they used to be.
As we age, learning new things become harder, not because we are getting stupid, but because learning new things is intrinsically hard. Almost all people get into a profession in their early 20s, but it becomes harder to change their career later in life. The reason is that they have more things on their mind to worry about as opposed to the early phases of life.
One does not stay young forever. And you cannot point out one or two or ten things which makes learning new things hard. It is a combination of many factors. That being said, becoming a pilot in your 50s or 60s is harder than in your 20s or 30s, but there are many old pilots who can do and have done things which younger ones cannot do. Example: Captain Sully
You can ask why most athletes are in their 20s, not in their 60s, and will get a similar answer.

Seems like everyone has taken my question as some sort of "old vs. young" thing. Totally not what I intended. It's obviously a fairly solid fact that younger flight students progress more quickly through training than older ones. I could dig up a few quotes from CFI's right here on av.se and numerous from online. It's really not a shocking concept. I'm just trying to get an idea from CFI's if there seems to be a particular area that takes people longer. The example of Sully is really not relevant, as he had been flying for 40-some years when the incident occurred.

Finished flight school 2 years ago. Youngest 16, oldest 75. The older guy did absolutely fine and being calm and a good observer turned out a good glider pilot. Still, as one would expect, it took him a lot more that the guys in their 20s to learn all the mnemonic stuff and to become good at the manouvers where physical "feel" is important (sideslips and co.)


text:
Why do people put $1 & OVC on aircraft bills of sale?
When purchasing an aircraft a bill of sale is created to show transfer of ownership from the seller to the buyer. Bills of sale include what the seller was paid in exchange for the plane. But apparently bills of sale for aircraft are commonly done differently.

The first item to fill in is the price of the aircraft, where it says "For and in consideration of $___." To preserve the confidentiality of the transaction, the FAA will accept the phrase “$1 & OVC” (Other Valuable Considerations) in this spot, and most Bills of Sale are filled out in this fashion.
  source

At first I thought maybe it was some way to get out of sales or use tax, but the FAA would certainly not approve tax evasion. The state will calculate taxes either from the lien amount or the usual market value. This would definitely not pass muster for the sale of a car or a house. The only time the state treasurer ever had me put $1 was when I was giving a car to a family member.
Obviously the price is being withheld for some reason, but I can't really figure out what that reason is. The price is easily found with a records search. The only person this hides the sale price from is the FAA. And since the FAA approves that wording they obviously don't care. Why do people not want the FAA to know how much they paid for their plane?

As someone living in Europe, I have absolutely no clue what you are asking. Would be nice if you could provide some context.

Why would you want anyone to know how much you paid for your plane?  Or anything: the "$1 & Other Valuable Considerations" is quite common in all transactions between private parties.

I suspect this is a general contract law question that might get a better response on law.SE

@J.Hougaard Sorry. I had a bunch of trouble getting the friggin dollar signs to render on the quote that I forgot to put in the first paragraph

@Pondlife Maybe so, but I'm wondering if there is an aviation-specific reason. I've never seen that done on a car or a house, for example.

It's common with car sales as well (private sales at least). It can avoid massive registration fees and taxes, which are based on the last-sold value of the vehicle (so $1 sale on paper gets minimal fees)... obviously, your personal ethics would have to be a factor.

I do not know if used for the same purpose but I have seen the same in other contracts, as FAA is contracted by 1$ they have a contract and a obligation to commit to the contract. So including that small amount is a way to bind legally.

This practice is really more of an accounting/finance question than an aviation one, but it's common enough that it's probably worth addressing here.
When reviewing an aircraft's registration record you will frequently see the price on the FAA Aircraft Bill of Sale form given as "\$1.00 & OVC" (One dollar and Other Valuable Consideration) as shown on the example below (click to enlarge).

The "Other Valuable Consideration" can be anything of value: Personal favors, other property (a car, a different airplane), blackmail information on someone you don't like, or (most commonly) money in excess of \$1.
In a strict cash sale recording the amount on the bill of sale in this manner protects the sale price from prying eyes: Anyone with \$10 to spend can request an aircraft records dump from the FAA which will contain every bill of sale filed, but if the price is listed as some small dollar amount plus "Other Valuable Consideration" it's impossible to determine the exact price paid using only the bill of sale.
Note that in cases other than a strict cash sale other documents filed with the FAA (for example recording a lien against the aircraft to secure a loan financing the purchase) may disclose the purchase price depending on how those documents are filed: Some include the amount of the debt the aircraft is securing, others simply state "The debt identified by loan number 12345." which would still protect the confidentiality of the sale price.

As a means to avoid taxation recording the sale price as "\$1 & OVC" almost never works: The tax authority is going to ask you the value of the "Other Valuable Consideration" and base the tax due on that amount.
If you tell the tax authority the aircraft was really only worth $1, and record it as such, they're going to want to know why: Generally even an unairworthy aircraft is worth more than that for the value of its parts.
Conversely if you get a ridiculously good deal on an airplane it can be to your advantage to fill out the bill of sale accurately & present that along with other documents pertinent to the sale to your tax authority: You may be able to get the sales/use tax based on the ridiculously good deal rather than an appraised market value.

Is there any reason not to simply write "confidential" or "not disclosed" instead of this useless mention? In France, writing "1€" would just mean 1€ exactly.

@mins In US contact law there has to be "consideration" for any contact to be valid. Like voretaq said, that can be in any form, but if you can't really specify what intangible things there are then courts have ruled that $1 satisfies the "consideration" test. When my dad gave me his car once the state treasurer's office had me write up a bill of sale for\ $1 just to make the transaction legal and binding

@mins And, btw, yes I did have to pay the 6 cents sales tax


text:
What is profile drag?
I know about induced drag, parasite drag, form drag, skin drag, wave drag, and interference drag. But I don't encounter the term profile drag often, and I can't find a good definition of it.
Is profile drag the same thing as form drag? If not what is it?

And exactly what type of drag is RuPaul?

It's the observation that when you run code under a profiler to measure its performance, the very act of measurement causes it to run slower, or "drag".

@hobbs lol no kidding

Yet another breakdown for drag.

@mins Threre are so many different types of drag that trying to understand is really becoming.... [ok, did anybody not see this pun coming?]

The composition of total Drag as it is shown below:

Thanks to DRAGBUSTERS... This document can solve this question, and analyses the drag in detail.

Profile Drag Definition:
  Profile Drag is the drag incurred from frictional resistance of the blades passing through the air. It does not change significantly with angle of attack of the airfoil section, but increases moderately as airspeed increases.
   Taken from here.

Definitions of profile drag as they are in dictionaries:

The portion of the wing drag that is due to friction and turbulence in
  the fluid and that would be absent if it were nonviscous
The part of the drag on an aerofoil or aircraft which arises directly
  from its profile and from skin friction (i.e. the part not
  attributable to lift).

By reading this...(in fifth par.)

Form Drag Definition: Drag which depends on the shape of the aircraft, is called form drag.

The following definition has been taken from here.

Profile Drag or, sometimes called form drag, is the drag
  caused by the separation of the boundary layer from a surface and the
  wake created by that separation. It is primarily dependent upon the
  shape of the object. Form or pressure drag is caused by the air that is flowing over the aircraft or airfoil.

And finally, the most commonly types of drag encountered are,

Parasitic Drag, composed of

Form Drag, which is the result of the aerodynamic resistance to motion due to the shape of the aircraft,
Skin Friction Drag, which is due to the smoothness or roughness of the
    surfaces of the aircraft, and
Interference Drag, which may occur where surfaces with different characteristics meet (e.g. wing and fuselage)

Induced Drag, which is a secondary effect of the production of lift,and
Wave Drag which comes into play when shock waves are developed close to the surface of the aircraft in transonic and supersonic flight.
Taken by this Skybrary Article which describes very nicely the types of drag.

Herein lies the conundrum. I posted the question after having read most of those articles. They each give s different definition. Your first example basically gives the definition of skin drag. Your second example first appears to define skin drag, then changes and defines it as the sum of skin and form drag. The third is actually defining form drag, not addressing profile. The fourth says it's another name for form drag. And Skybrary never mentions profile at all. So my question is still not answered.

Why would induced drag flatten at low speed? Those two plots look very wrong near the Y-axis. Apart from that your answer is spot on.

Thank you for your comments, the answer is revised, with new content. Hope this helps now. If you need anything else, or if something is wrong, please let me know.

Ok, I think the flowcharts are going to be the key to understanding it. +1 for those. Can you look at the other definitions in your answer? Some seem to conflict with the chart and should probably be edited out. For example, it's clearly not synonymous with form drag and one of the definitions says exactly that

Yes of course, there is a sense of contradiction between the definitions, but at the same time, if you see the second flow-chart, imho, the definition is not actually completely wrong, but it depends on the perspective of taking a UNIT(profile or form, or all together), for a measurement, and of course it depends on the perspective of 2D and 3D. I am going to make an edit on this, to look right,but  if you still think that is not correct please point me out, the section, that you think, needs an edit.

I share your confusion about those many sources of drag.
In the end, many of them describe similar things. When doing a performance calculation, it is extremely important to add all drag sources and to do this for every one only once. Drag estimation requires meticulous bookkeeping. Therefore, I would distinguish only two types of drag:

Viscous drag, where the flow is slowed down by friction. The result is a force parallel to the local surface, and viscous drag is its component parallel to the flow direction at infinity.
Pressure drag, where the local lift vector is tilted away from the vertical (in reference to the flow direction at infinity).

Profile drag is a muddle because it adds both types, but only part of them. This makes proper bookkeeping harder. As Trebia Project writes, profile drag is the drag in 2D flow and neglects both interference and lift-related components. But when designing an aircraft, profile drag is easy to get at - just look it up or run a calculation.
Profile drag includes the full friction component of the unswept wing without engine and real-world effects (so no drag from flap gaps, pylons, flap track fairings, rivet heads ...), the pressure drag from incomplete pressure recovery and wave drag in supersonic flow. It excludes the lift-related drag (induced drag) in subsonic flow, the pressure drag stemming from interference and the drag increase in the slipstream of a propeller. All these drag sources need to be added and be kept free of drag that was already considered in the profile drag data.

So that's why I don't run across the term often, because the components of profile drag are accounted for by the other terms?

@TomMcW: Yes, the same drag is called friction drag plus form drag or whatever expression the author picks. Profile drag has its justification because it can be looked up easily during early design and the expression should occur most often in this context.

I have seen this term wrongly used.
The right definition refers to the drag of an aerodynamic 2D profile. Essentially, friction drag and form drag, ignoring the induced drag being a 3D phenomena.
However, in some papers I have seen the use of this term as equivalent to the form drag itself, not being restricted to a 2D phenomena.

A 2D object as viewed from what angle? From the direction of the airflow or orthagonal to it?

Essentially a cut of the wing perpendicular to its length axys.

Profile drag is the combination of form drag and skin friction as it results from the cross-sectional area, or profile, of the aircraft, presented to the relative airflow.
Principles of Flight | ATPL - Lesson 6 Part 2 - 7:34

The total drag acting on an aircraft in flight is the sum of:

Profile drag
Induced drag
Interference drag

Profile drag can be further separated into:

Form drag
Skin friction drag

Form drag is produced whenever the streamline airflow passing over an aircraft separates from the surface and becomes turbulent. An example of extreme form drag is the effect of a flat plate placed at right angles to the airflow:

Skin friction drag is a function of the layer of air closest to the surface. As air flows over a wing, the roughness of the surface and the viscous property of the air itself slow it down. Much like other fluids, the more viscous the air, the greater its retardation. At the surface, the air particles adhere
to it and their relative velocity is reduced to zero:


text:
Is the yaw damper on modern airliners safety critical?
Question is inspired by the recent Southwest 737 MAX Dutch Roll incident. The news articles said the crew "regained control", which implies that the aircraft was out of control prior. I did some reading and saw that the 757, 747, and other current airliners are allowed to take off with one yaw damper that's inoperative (out of a total of two). There's even a button to turn it off. Browsing the Reddit threads on the recent Southwest 737 MAX incident, I have heard conflicting reasons for the yaw damper. Some say that the plane will shake itself apart because these jets cannot naturally fly straight without a computer (yaw damper), others say it's just for passenger comfort and isn't a safety item. It would seem rather concerning if Boeing designed a jet that's so inherently unstable that it'll depart from controlled flight without a computer band-aid fixing the instability.

"The news articles said the crew "regained control", which implies that the aircraft was out of control prior." – No, it does not. It implies that the author of the article, who is most likely not an expert in aviation, thought that this wording would sell the most ads.


text:
What could explain that small planes near an airport are perceived as harassing homeowners?
My friend lives near a smaller busy airport and told me she's getting the feeling that pilots of small propeller planes are purposely flying very fast and loud around her neighborhood sometimes 4 of them at a time. She says they start as early as 6am and go as late as 12 midnight.
I've been been at her home when this has happened and some of the planes are really loud. Sometimes they do this for hours at a time. Other pilots fly over and are not nearly as loud and you don't even notice them unless you happen to look up and see them.

Knowing some tail numbers would help us see if the planes are flying in normal boring ways or if there’s truth to this.

6am to 12pm sounds more like the schedule of a relatively big hub than a small GA airfield. I'd check with the local authorities it there's a time (and noise) limitation in force.

@sophit I'm not sure about OP's location, but many GA airports in the U.S. are not small and few (even of the small ones) have time restrictions or noise restrictions that have significant applications to small, propeller-driven aircraft. Some U.S. GA airports can actually have more flight operations than some airline hubs. Van Nuys airport (in Los Angeles) has had as many as 600,000 annual flight operations in the past. To put this into perspective, London-Heathrow had 454,000 last year.

I would also note that it is exceedingly unlikely that any aircraft (propeller-driven or otherwise) is flying fast (for their airplane) near an airport. Takeoff and landing and typically the slowest parts of a flight and both climb-out and final approach have particular (and relatively slow) speeds that pilots will always fly during those phases of flight.

I have a coworker who's learning to fly right now and he's doing the lessons early in the morning before work, because it's cheaper and convenient for traffic heading to work. So 6am flights will not be unusual if there's a flight school.

@reirab "Prior to May 2011, […] numbers included flights that transitioned into VNY airspace, including flights to Burbank. As of May 2011, VNY no longer includes [these], and instead only reports actual takeoffs and landings at VNY." But it's still an impressive number.

@Bergi Right, but, if you look at the year where that transition happened, it only dropped the number by about 40,000, so still probably a good 550+k daily flight operations at the peak.

@Eugene Night flying is also relatively common if there are flight training operations because night flying is a required part of flight training. Also, there doesn't need to be an actual flight school in order to have flight training operations. CFIs can do flight training at nearly any airport, other than a few of the busiest ones. The airports I flew out of when doing flight training are relatively small GA fields that don't have any formal flight school. At least here in TN, flight training seems to be common at most public GA airports.

There is another neighbor who has videos posted on Facebook and the airport location. The airport is Oakland County International Airport in Waterford Michigan. https://www.facebook.com/groups/857372182865064/

Person buys/rents home near a busy airport. Sometime later, person is annoyed airplanes are flying in and out of said busy airport. Amazing...

It's not intentional. Small airports have a traffic pattern -- think of a rectangle where one of the long ends is the runway. Airplanes fly this pattern when landing, and student or private pilots will frequently fly circuits of this pattern to get additional practice landing. As you noted, sometimes several airplanes will do this at a time.

Traffic Pattern (image from the FAA Airplane Flying Handbook)
Airplanes make more noise when they're climbing than when they're descending. If your friend's neighborhood is beyond one end of the runway, some of the time airplanes will overfly the neighborhood while they're taking off. Which direction airplanes take off is influenced by which direction the wind is blowing. They're not being loud over your friend's neighborhood out of spite, they're being loud because the wind is coming from the west rather than the east (for example).
Additionally, some airplanes are simply louder than others.
Takeoff and landing are the most demanding phases of flight. A pilot is not going to spend the mental energy intentionally bothering the people who live near the airport (for what reason?). They're focusing on getting off the ground or back on the ground safely and efficiently.
If this small airport has a flight school, perhaps your friend could inquire about a "discovery flight", to see what flying entails. She could converse with an instructor about planes overflying her neighborhood to see what they're doing there.

Well, I think it is a truism that noisy things closer to you are noisier yet, and aircraft at lower heights landing and taking off will sound louder to the neighborhoods nearest the ends of the runways. For practice and learning and staying current pilots will often fly circuits and touch and goes (rapid landing/takeoffs) no doubt from time to time this can become irritating.

A small training plane costs at least $120 per hour to rent, so most pilots are not going to waste time in the air just making noise to piss people off.
Now if the airport in question hosts a flight school, then the student pilots taking lessons there will make landings and takeoffs over and over all day long, flying the same pattern around and around again, until they get proficient.
Even after they obtain their licenses, they will still spend hours at a time doing nothing but takeoffs and landings - which are called "touch & go's" because as soon as the plane's wheels are rolling on the runway, the pilot revs up the engine and does a takeoff without even coming to a halt, to get the most possible landings and takeoffs per hour of plane rental time.

Have pilots intentionally looked to overfly a specific property? Almost undoubtedly - and I'd suggest probably routinely in multiple places around the world.
Was it done with harassment in mind? possibly, but probably rarely.

One notable example in the UK is a popular TV personality, turned farmer, Jeremy Clarkson.
He has on many occasions reported light aircraft pilots intentionally (in his opinion) flying low over his farm in the Cotswolds. This has lead to news stories in the national press.

One of the pilots claimed to investigators at the UK Airprox Board that he believed the person flying the other aircraft "was looking to manoeuvre over a noteworthy property" when the near-miss incident occurred.

Over the weekend, the presenter took to Twitter to share his annoyance at someone flying over his farm.
Jeremy penned: “Quick message to the chap flying in circles 500 feet above my house: f*** off.”
Fan @davroschief1 then responded to the star about the issue.
They penned: “It’s legal Jeremy (unfortunately).”
The petrolhead then hit back: “It’s legal. But selfish.”

Oh the irony of Clarkson being annoyed by what someone else is doing

He could use the Welsh approach to deterring aircraft: https://www.targeta.co.uk/wheretogo.htm

Most pilots I know, including myself, don't want to annoy the community due to the potential of the airport ending up closing and being sold to a developer for housing or a mall.  Some airports have published "noise abatement procedures", which are specific instructions to avoid noise-sensitive areas.  You can contact the local FAA FSDO office to inquire about this:
https://www.faa.gov/about/office_org/field_offices/fsdo
See also: https://www.faa.gov/faq/what-noise-abatement-procedure


text:
Is a pilot's instinctive reaction to a stall counter-intutive?
Is the correct stall recovery action somehow counter-intuitive? I've read about crashes like Colgan Air 3407 where pilots experiencing a stall have done the exact wrong thing and pitching the nose up. It makes me wonder if pitching down does not feel right to a person.
Not being a pilot I can only relate it to driving a car. You're taught that to recover from a skid you should steer into it. An inexperienced driver will be in a turn, feel a skid and turn the wheel further into the turn resulting in loss of control. You have to teach yourself to overcome that instinctive reaction and remember what you were trained to do.
Is the reaction to a stall similar? When you feel the a/c lose lift and start dropping is it an instinctive reaction to try to climb? You're going down and you want to go up so you pull back. Do you have to teach yourself to overcome a reflex to use proper recovery technique?
If so do airline pilots practice stall recovery in a simulator? I know it took me a bit of practice in an icy parking lot to make skid recovery come naturally.

"You're taught that to recover from a skid you should steer into it"... really? AFAIK not so in Italy. Safe driving is not taught in order to take the driving license. They just teach you how to accelerate/brake, turn, change gears, park. Hopefully pilots do more training than that.

No one teaches you that when taking driving lessons. Just if you go for an advanced driving course, that's the action they teach you there.

The correct way to recover from a stall is counter intuitive, not because pilots are trying to climb, but because the nose of the airplane drops due to the loss of lift and aircraft design.  99.999% of the time (when the aircraft is not in a stall), if the nose drops, you simply pull back in order to raise it and this muscle memory is built over time.
Unfortunately, if the aircraft has stalled, pulling back will only worsen the situation and you need to push forward in order to gain sufficient airspeed for a recovery.
Yes, stall recovery is taught in both primary training, and during simulator training for pilots, although not typically to a full stall in the simulator.  Instead, the aircraft is slowed to the first indication of a stall which may be a stall warning system instead.  At this point they are expected to apply the correct stall recovery techniques recommended by the manufacturer / their SOP's.
There is a fairly large difference between recovering from a stall in a training environment because you know that it is coming and already know what you are going to do when it happens.  A large part of stall training is for stall recognition so that hopefully if it were to happen outside the training environment, the pilot will recognize the warning signs before it happens and can apply the proper stall recover technique before the aircraft enters a full stall.
Unfortunately, out "in the real world" most unplanned stalls that occur happen because the pilot is distracted by something else and they aren't expecting it. That lack of anticipation sometimes causes them to fall back on muscle memory and pull up just because the nose fell without realizing what happened.  This can be more likely when the stall doesn't happen quite like it does in training.  In some situations there may be fewer warning signs, or a component of the stall warning system isn't working as expected and can delay the realization that they are in a stall.
For more information on what a stall is and why pilots practice them, see another question that was asked before here: What happens when an airplane stalls and why do pilots practice it?

Apologies for possible a dumb question, but are you sure that pilots in training are told what simulation they are going through before it occurs? That seems ridiculous.

@scott yes.  Stalls in sim training are purposeful, briefed maneuvers demonstrated to show proficiency.  The only other way they would happen is accidentally through pilot error and in the sim environment that is a ticket to more training.  To be clear, the sim instructor / APD will say e.g. "show me a right turning stall" and you will demonstrate that maneuver (or whatever variation he asks for).

Is it possible in a simulator to accurately simulate what a stall feels like? Some of the answers here are saying they simulate an 'impending' stall, such as warning horns. I doubt if very many pilots have experienced an actual stall in an airliner. It appears that the AF 447 crew were in a stall for 4 minutes with the stall warning going most of the time but never recognized what was happening. They disregarded the warning system. Apparently their training in stall recognition failed them.

@TomMcW: Simulator can't accurately simulate the drop when the aircraft accelerates downward because of loss of lift, since inertial forces can't be simulated. But it can simulate the buffeting that precedes it and the stall warning and it can simulate any changes in attitude.

@TomMcW Actually, one of the contributing factors in the AF 447 accident is that the stall warning was NOT going most of the time, and was inhibited due to the extremely slow airspeed (it was a design decision made because an airliner "can't" be flying at such a slow airspeed).  It came on in the beginning but then went off, and was one aspect that led to the confusion among the pilots.

@Scott While it may seem ridiculous, I can't think of a way to "accidentally" get the airplane too slow without the pilot noticing, and still be a realistic scenario.  Many other events in training are given to us without notice (engine failures, hydraulic failures, fires, etc. etc.) but a stall is really only caused by pilot error (short of catastrophic structural failure...).

@Lnafziger Pitot tube malfunctions (which can be simulated), maybe?

There are a few issues. First off everyone that has a pilots license (in the US at least) has stalled an aircraft (generally a trainer), its a requirement for obtaining the license. Commercial pilots also receive spin awareness and recovery training.
It should also be noted (as its sometimes overlooked)

A Stall can occur at ANY airspeed

A stall by definition is when there

...is a reduction in the lift coefficient generated by a foil as angle
  of attack increases

You are correct that sometimes people pull back on the controls (nose up) when a stall occurs. This is why stick shakers and pushers exist. Its not very instinctive to push the stick and subsequently dive the airplane towards the only real obstacle, the ground. The problem, sometimes is recognizing that the aircraft is stalling (one of the issues in the Air France 447 crash) failure to do this can lead to the pilot making the wrong corrective action because they don't know what is really happening to the plane.
In the case of 3407 it seems the pilots first mistake was not maintaining proper approach speed. The second mistake was not applying full throttle during the recovery and pitching the aircraft up to much. This put the plane into the stall which they could not recover.
Although only touched on in the Wiki article, the pilots did report Ice (although de-ice was activated) it should be noted that ice build up on the wings alters the stall and flight characteristics of a plane. On a similar note, both wings often do not stall at the same time. The drop a single wing during a stall can also lead to counter control that causes issues.

I think you're on to something with the wing drop or other aerodynamic effects. Most pilots have no problem recovering from a straight and more or less level stall-horn warning. It's when you get weird behavior from your aircraft that instincts cross you up. Wing drop is a good example, trying to counter it with aileron will drop the ailerons on the stalled wing causing more drag and further pushing it into the stall and impending spin. Likewise, an unexpected nose-drop can cause the instinctive reaction to pull back.

Although I am not an official on the matter my reading of the accident leads me to feel that (although not the only factor) ice may have played a roll in what happened to 3407.

To clarify here, there are usually a multitude of factors contributing to stall problems in commercial aircraft. In non-commercial aircraft the airfoil could be at an extreme angle but you could have more than enough airspeed to compensate for the given airframe -- like a stunt pilot doing doing a loop. In training the instructor stalls by slowing down and pulling up the nose when you're plenty high enough to recover. But in a commercial craft, the pilot could have more than enough airspeed and a normal attitude but something else is compromising the airfoil (landing gear, ice).

Just to second Dave's answer, typically a pilot who pulls up in stall does not realize that they have stalled and are just blindly reacting to a loss in altitude. To answer your specific questions:
Do you have to teach yourself to overcome a reflex to use proper recovery technique? Not really. Most dangerous stall situations are confusing enough that there is no "reflex", it's just a question of whether the pilot is calm enough to use their training and knowledge. An untrained person will just freeze or manipulate the controls wildly, there is no "reflex". Most fatal stalls occur close to the ground where even the correct reaction will come too late or in low-visibility conditions in which the pilot cannot see the horizon. It is pretty rare for a pilot who can see the horizon and has plenty of altitude to stall all the way to the ground.
The main benefit of training is not to overcome a reflex, it is to learn to react quickly to the situation, so you spend less time figuring out what is going on and react faster. Every pilot knows to push the stick forwards in a stall; the question is how fast do they realize they are stalled, and how fast do they react once they realize that?
...do airline pilots practice stall recovery in a simulator? Yes.

How unfortunate it is called "stall training" because I have never taught any of my students how to stall an aircraft!  I teach them to recognize the impending stall and how to fix it before the stall happens.  I show them a full stall and teach them how to recover.  It should be renamed "stall recovery training"  I try to surprise train also, during slow flight I keep stating they can fly slower and slower, I keep pushing to get them to fly slower....suddenly the plane drops out of the sky in an unexpected stall and they usually freeze for a couple of seconds then they recover.  Or during unusual attitude I will turn the controls over just as the plane stalls.  Point is, I focus more on recognition and recovery, than the stall itself.

As a pilot of a recreational aircraft (very small aircraft) I have become accustom to the feel of the aircraft in a stall. When the aircraft stalls, it drops suddenly. This is the same feeling as being in a rollercoaster that has just gone over the top and begun to fall.
My instinctive reaction in this case is to push the nose down. As soon as I have recovered from the disorientation of the stall (or turbulence which can cause the aircraft to drop momentarily), I can make better decisions.
I am fairly sure (without any research) that a large aircraft would not have this characterisic, and as such, the pilots would not develop an instinct for this.

A large aircraft will have similar feel, because the wings will loose some lift in the same way. However in large aircraft stall is more risky, so nobody practices stalls in large aircraft for real and simulator can't reproduce the feel well, because inertial forces can't be faked and even full-motion simulator can only drop a couple of feet.

There is one other thing to consider regarding stall training, namely how applicants for pilot certificates (especially at the Commercial and ATP level) are evaluated on their checkrides, which feeds directly into how they are trained.
The FAA is currently in the process of revamping its certification process with the Airmen Certification Standards replacing the old Practical Test Standards for the "checkride" (i.e. oral examination and flight test) portion of the certification process. However, one of the major differences between the Private Pilot level and the higher levels of certification was that, at the Private Pilot level, the testing standards called for

"[recognizing] and [recovering] promptly after a fully developed
  stall occurs"

Contrast with the evalution criteria for this maneuver at the Commercial and higher levels, where the applicant is expected to

"[recognize] and [recover] promptly at the “onset” (buffeting)
  stall condition"

Now, if you've followed the second link, you will also see a note immediately below that states:

Evaluation criteria for a recovery from an approach to stall
  should not mandate a predetermined value for altitude loss
  and should not mandate maintaining altitude during
  recovery. Proper evaluation criteria should consider the
  multitude of external and internal variables which affect the
  recovery altitude.

That addition is relatively recent. I don't have a PTS from circa 2007/2008 (when I was going through my own SEL and MEL Commercial training) handy, but I do not remember that section being there. In fact, the way evaluation criteria had evolved "in practice", was that any altitude loss during the maneuver was grounds for failure of that portion of the test.
On the one hand, that led applicants to be extremely proactive and initiate recovery the instant they felt a buffeting or they heard the stall warning horn going off. On the other, it also led applicants to recover by advancing the throttle to full and unloading the wing only the absolute minimum amount needed to avert an immediate stall, preferring a prolonged low-energy state over the altitude loss that a greater degree of unloading would have brought, even though unloading the wing more would have allowed the aircraft to accelerate out of the low-speed regime quicker.
Training is habit-forming (that's the whole point, after all) and that particular habit is now recognized to be dangerous enough that the FAA has both addressed it in the PTS and issued guidance to DPEs on the matter.
The Captain and FO on the Colgan flight, however, did their initial and recurrent training under the older way of doing things and likely picked up some habits that got them through their checkrides but where woefully lacking in a real-world scenario where they fell behind the airplane and found themselves in an actual stall, rather than at the "outset" of one.


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What is an Enhanced Vision System?
I was reading something at work that said the company has installed an Enhanced Vision System on the aircraft.

FedEx Express added Enhanced Vision Systems to 250 aircraft, which will greatly improve pilots’ ability to land in low visibility conditions and mitigate potential weather delays. The company is the only U.S. carrier with FAA approval to use the technology as low as 100 feet on instrument approaches.

What is this system and how does it work? Is it some type of FLIR?

It's essentially a combination of the capabilities of FLIR and NVG's, although built into the aircraft and displayed in the HUD rather than worn as goggles.
FLIR, short for Forward Looking Infra Red, uses far-IR to see the heat of terrain, and essentially turns the night into day, at least for the field of view that it "sees."  NVG's (Night Vision Goggles) use near-IR and magnified visible light.  The near-IR doesn't see terrain except to the extent that it's illuminated by something (moonlight, starlight), and far-IR can't do much to tell the difference between a light that's on or off (so you can see the runway edge, but you can't see the runway edge lights using FLIR, for instance).
The two systems have slightly differing capabilities and limitations; when both are fused together onto a display (i.e. a Heads-Up Display, or HUD), the pilot gets a pretty amazing picture of what is directly in front of him: the far IR shows him the runway edges, taxiways, pavement, buildings, obstructions,etc, and the near-IR makes lights (i.e. runway and taxiway lights) stand out.  In low visibility, the far-IR tends to be somewhat more degraded than the near-IR, whereas at night & with no moon, the near-IR shows the lights but not much else.  Together, the pilot can get the runway lights in sight sooner than he could unaided, and by the time he's landing he can see "everything" in the field of view of the HUD, not just the lights themselves.
Example videos:

YouTube
Vendor's Website
AvWeek

When the videos get down close to the runway, you can pick out the glowing approach and runway lights, which is where EVS differs from pure FLIR.  With FLIR, you'd see (sort-of) the lights and any framework that they're mounted on, but they wouldn't particularly glow -- they might as well be off.  With EVS, the crew can fly a CAT I ILS and actually have the approach lights, runway, runway lights, etc all in sight at the 200' DH, even when the visibility is such that with the naked eye, none of that would be visible.  At major US airports, CAT III approaches are often available, but elsewhere they may be rare or nonexistent.  The EVS capability has the promise of allowing crews to successfully land out of a Cat I approach (i.e. at an airfield that only has Cat I ground equipment) even in Cat III weather; from the OP's quote, it looks like they already have approval to use it for Cat II conditions. And for a global carrier like FedEx, that's a capability worth having.